This invention relates generally to the field of intraocular lenses (IOL) and, more particularly, to multi-lens IOLs.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens.
Prior to the present invention, when a cataract or other disease required the removal of the natural lens and replacement with an artificial IOL, the IOL was a monofocal lens. Most IOLs are sold in power increments of +/−0.5 diopters, and the ultimate power of the lens depends upon where the lens sits along the optical axis. The fixed increment of the lens, and the slight variation in lens placement can result in less than optimum vision. Although this situation occurs relatively infrequently, and generally is not severe, some patients ultimately are required to use a pair of spectacles or contact lenses for optimum vision. If the power of the implanted lens is incorrect, removal and exchange of a new lens is difficult because of fibrosis of the lens haptics within the capsular bag.
There have been several prior suggested adjustable power IOLs, none of which have been commercially introduced. For example, U.S. Pat. No. 5,222,981 (Werblin) and U.S. Pat. No. 5,358,520 (Patel), the entire contents of which being incorporated herein by reference, suggest the use of a second or even a third optic that may be implanted and attached to a previously implanted primary optic so as to adjust the overall optic power of the multi-lens system. U.S. Pat. Nos. 5,628,798 and 5,800,533 (Eggleston, et al.), the entire contents of which being incorporated herein by reference, disclose a threadedly adjustable IOL wherein the location of the optic along the visual axis may be adjusted. U.S. Pat. No. 4,575,373 (Johnson), the entire contents of which being incorporated herein by reference, discloses an IOL having an optic and an outer ring and connections between the optic and the outer ring made from a heat-shrinkable plastic. The connections are heated with a laser to adjust the power of the IOL. U.S. Pat. Nos. 4,919,151 and 5,026,783 (Grubbs, et al.), the entire contents of which being incorporated herein by reference, disclose a lens made from a polymer that swells or otherwise changes shape. The lens is implanted or injected into the capsule bag and selectively polymerized so as to adjust the power of the optic. U.S. Pat. No. 5,571,177 (Deacon, et al.), the entire contents of which being incorporated herein by reference, discloses an IOL having haptics with frangible stiffeners. Once implanted in an eye, the stiffeners are selectively cut or heated above their tg by laser radiation, causing the stiffness of the haptic to change and adjusting the location of the lens within the capsule bag. The multi-lens designs and the threadedly adjustable designs are not optimized for the reduction or elimination of posterior capsule opacification (PCO).
Therefore, a need continues to exist for a safe and stable intraocular lens system that provides adjustment of lens power.